Why does Thomson scattering cause polarisation?

Answer 1

The elastic scattering of electromagnetic radiation is Thompson scattering.

In the low-energy limit, the electric field of the incident wave (photon) accelerates the charged particle, causing it, in turn, to emit radiation at the same frequency as the incident wave, and thus the wave is scattered. Thomson scattering is an important phenomenon in plasma physics and was first explained by the physicist J.J. Thomson. As long as the motion of the particle is non-relativistic (i.e. its speed is much less than the speed of light), the main cause of the acceleration of the particle will be due to the electric field component of the incident wave, and the magnetic field can be neglected. The particle will move in the direction of the oscillating electric field, resulting in electromagnetic dipole radiation. The moving particle radiates most strongly in a direction perpendicular to its motion and that radiation will be polarized along the direction of its motion. Therefore, depending on where an observer is located, the light scattered from a small volume element may appear to be more or less polarized.

So basically, photons hit particles, those particles gain higher levels of energy, that energy radiates at a right angle of the motion of the particle, making it polarised in the in the direction the of motion.

So the polarisation is due to the increase of energy, by radiation.

di·pole1noun

1.

Physics, Electricity . a pair of electric point charges or magnetic poles of equal magnitude and opposite signs, separated by an infinitesimal distance.

Examples of Thomson scattering

The cosmic microwave background is linearly polarized as a result of Thomson scattering, as measured by DASI and more recent experiments.

The solar K-coronais the result of the Thomson scattering of solar radiation from solar coronal electrons. NASA's STEREOmission generates three-dimensional images of the electron density around the sun by measuring this K-corona from two separate satellites.

In tokamaks and other experimental fusion devices, the electron temperatures and densities in the plasma can be measured with high accuracy by detecting the effect of Thomson scattering of a high-intensity laser beam.

Inverse-Compton scattering can be viewed as Thomson scattering in the rest frame of the relativistic particle.

X-ray crystallography is based on Thomson scattering.